In the conventional Oldham coupling, projections formed in the end surfaces of shafts, and grooves formed in the intermediate disk are machined to a high accuracy, and the grooves of the intermediate disk are formed so that the bottom walls of the grooves are extremely rigid, to ensure an accurate transmission of a rotation of one shaft to the other.
However, the projections of the shafts and the side surfaces of the grooves of the intermediate disk are abraded in an extended period of operation due to the sliding movement of the projections and the intermediate disk relative to each other, and consequently, the clearances between the projections and the grooves increase to cause a loss of motion, which deteriorates the accuracy of the rotation.